Synthesis and effects of variations in tetraethyl orthosilicate and the hydrophobic agent hexamethyldisilazane on the characteristics of chitosan–silica aerogels

Oil spill contamination remains a major environmental issue due to the persistence and hydrophobic nature of petroleum pollutants. This study aimed to synthesize and analyze performance of chitosan–silica aerogels as eco-friendly sorbents, focusing on the effects of tetraethyl orthosilicate (TEOS) content and hexamethyldisilazane (HMDS) modification. Aerogels were prepared via a sol–gel method with TEOS volumes of 2, 4, and 6 mL, followed by freeze-drying, and modified using HMDS (0.5–2 mL). Structural properties were analyzed using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM), while oil absorption was tested using diesel oil. Results show that TEOS and HMDS significantly affect pore structure, surface chemistry, and absorption capacity. The best performing aerogel within the tested range (2 mL TEOS and 0.5 mL HMDS) achieved the highest absorption capacity of 779.10%. In addition, the FTIR confirmed that siloxane network formation and hydrophobic methyl groups, while the SEM revealed improved pore distribution. As a whole, these findings highlight the potential of modified chitosan–silica aerogels as effective, environmentally friendly oil sorbents, with reusability performance to be established in future work.